Vesicoureteral reflux is a congenital defect seen in both boys and girls that causes these children to be prone to febrile urinary tract infections. In vesicoureteral reflux, urine is propelled up the ureter toward and most times to the kidney by the increasing bladder pressure that precedes and accompanies urination. If left undiagnosed, this condition will lead to hypertension and/or kidney failure (in severe cases). Hence, it is extremely important to provide means to detect and monitor vesicoureteral reflux (VUR). The condition spontaneously resolves at a rate approaching 20% per year for lower grades of reflux, but many patients will require surgical repair or indefinite antibiotic therapy. Patients are treated with antibiotics during the condition, and the antibiotics discontinued when the condition resolves.
The most common current technique for the diagnosis and monitoring of vesicoureteral reflux is the voiding cystogram. This technique requires catheterization of the urethra, followed by filling the bladder through the catheter and fluoroscopic imaging during urination. A like procedure may be performed under a gamma camera employing a Tc99 radionuclide, which reduces radiation exposure but maintains the invasive nature of the study. There are numerous problems with such techniques: the children are required to undergo a painful and traumatic catheterization; the children are exposed to potentially harmful ionizing radiation, and the procedure is expensive to perform (being dependent on expensive imaging equipment typically housed at a hospital). Hence, patients seek to avoid this test. Risks associated with skipping tests are, however, scarring of the kidney, hypertension, renal failure, and infection (including death in serious cases). This test is so common that a small children's hospital in a mid-sized city can perform on the order of 1500 voiding cystograms each year.
Indirect cystography systems for detecting VUR utilize an injected contrast media, such as a Technetium 99 radionuclide, that fills the bladder after being processed through the kidneys. This technique eliminates the need for catheterization, but decreases the sensitivity of the test by 33% in the process. Further, the child must have an intravenous catheter inserted and is still exposed to ionizing radiation.
Ultrasound imaging systems for detecting VUR require neither catheterization nor radiation exposure, but are not reliably effective as diagnostic tools due to low sensitivity. See, e.g., C. Blane, Renal Sonography is Not a Reliable Screening Examination for Vesicoureteral Reflux, J. Urology 150, 752-755 (Aug. 1993). In addition, ultrasound studies are difficult and time-consuming to perform. Indeed, standard voiding cystograms are recommended for confirmation even if an ultrasound is highly suggestive of VUR.
In view of the foregoing, there is a continued need for a simple and reliable way to detect vesicoureteral reflux that does not require catheterization, exposure to ionizing radiation, or expensive imaging hardware.